SEPA
United States
Environmental Protection
Agency
Municipal Environmental Research
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/D-83-117 Oct. 1983
ENVIRONMENTAL
RESEARCH BRIEF
Chemical Reactions of Aquatic Humic
Materials with Selected Oxidants
R. F. Christman1, J. D. Johnson, D. S. Millington, and A. A. Stevens2
Abstract
A study was conducted to identify the specific organic
reaction products of natural aquatic humic materials with
selected oxidants (KMnO*, HOCI, CI02, O3, and mono-
chloramine). Fulvic and humic acid fractions were isolated
from two southeastern U.S. surface waters using a
combination of XAD-8 adsorption, acid precipitation, salt
removal, and freeze drying. One or both fractions were
exposed to each oxidant under controlled laboratory
conditions at various oxidant/carbon molar ratios (KMnO4,
0.75 to 2.2; HOCI, 4; CI02, 1.0; 03, 4.8 to 7.3; mono-
chloramine, 2.0 and 10.0). The principle objective was
qualitative identification of reaction products; therefore
strict efforts were not made to use reactant concentrations
at water treatment plant levels or to keep oxidant/carbon
ratios at identical levels for the different oxidants studied.
Reaction products were identified by gas chromatography/
mass spectrometry (GC/MS) after solvent extraction and
derivatization. The two most reactive oxidants in terms of
the number of identified products and overall yields were
KMnO* and HOCI, though products were identified after
exposure to CI02 and O3. Certain similarities exist among
the oxidation products identified from all oxidants, though
the presence of chorine in reaction products depends on its
presence in the oxidant.
The macromolecular structure of aquatic humic and fulvic
acids (inferred from the nature of NaOH and KMnO4
degradation products) may consist of (a) single-ring aro-
matics with mainly three to six alkyl substituents, carboxylic
acid, ketone, or hydroxyl groups, (b) short aliphatic carbon
'University of North Carolina at Chapel Hill, NC 27514
2Municipal Environmental Research Laboratory, USEPA, Cincinnati OH
45268
chains, and (c) polycyclic ring structures, including poly-
nuclear aromatics, polycyclic aromatic-aliphatics, and fused
rings involving furan and possibly pyridine. Though the
structural relationships between these fragments could not
be established, these fragments are believed to be associ-
ated with humic macromolecules through carbon-carbon
linkages.
The degradation products of fulvic and humic fractions from
two water sources were qualitatively similar to each other,
but some quantitative differences were found. The dif-
ferences found between fulvic and humic fractions isolated
from each source were smaller than the differences
between the fractions isolated from the different sources.
The principal identified chlorination products of the fulvic
and humic acid samples studied were, in order of decreasing
abundance, trichloroacetic acid, chloroform, and dichloro-
acetic and dichlorosuccinic acids. For fulvic acid, the total
yield of identifiable products was approximately 14 wt% of
organic reactant (compared with 25 wt% for KMnO<). The
principal products accounted for approximately 4 wt% of
original total organic carbon (TOC). Of these, product
composition was approximately 69% trichloroacetic acid,
19% chloroform, 9.5% dichloroacetic acid, and 4.5%
dichlorosuccinic acid, based on product carbon per gram of
starting fulvic acid. Thus trichloroacetic acid (not chloro-
form) was shown to be the dominant chlorination product.
Collectively, these four products accounted for 53% of the
system total organic halogen (TOX).
Chlorine dioxide produced fewer identifiable reaction
products than chlorine, with product composition domi-
nated by C-i-Ciodibasic aliphatic acids. Chlorinated products
of CI02 included trace amounts of dichloroacetic acid.
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monochloromalonic acid, and monochlorosuccinic acid. No
products of the reaction of monochloramine with f ulvic acid
were identified by GC/MS.
This Research Brief was developed by the principal
investigators and EPA's Municipal Environmental Research
Laboratory, Cincinnati, OH, to announce key findings of the
research project that is fully documented in the reports and
publications listed at the end.
Introduction
Humic substances account for significant but variable
proportions of the organic matter in soils and sediments
and of the soluble organic matter in fresh and sea waters.
Despite extensive research concerning the formation and
environmental impact of waterborne organics, the chemical
structures of aquatic humic substances are still not known
to the desired level of certainty.
These natural products are apparently acidic, hydrophilic,
complex materials that range in molecular weight from a
few hundred to many thousands. Humic materials isolated
from soils have been extensively studied, but it cannot be
presumed that aquatic humic materials are similar except
for chemical complexity. Degradation studies of soil humic
acid have produced evidence of both aromatic and aliphatic
constituents, but few degradation studies have been
conducted on aquatic humics. Furthermore, it is not known
whether aquatic humic and fulvic materials isolated from
different sources exhibit chemical similarities.
Our experimental approach was therefore to expose natural
humic and fulvic acid preparations to a nonhalogenated
oxidant (alkaline KMn04) under controlled conditions.
Knowledge of the yield and reaction product distribution
should be useful for (a) increasing our understanding of the
macromolecular structures of undergraded humic and
fulvic materials, (b) determining the differences that may
exist between humic substances from waters of different
geographical locations, and (c) establishing a baseline of
oxidation products with which chlorination products can be
compared.
Certain experimental procedures are common to all aspects
of this research. The XAD-8 isolation/purification process
and the GC/MS systems employed are fully described in
project publications (6,8,11). Except where specifically
stated in these publications, GC/MS identifications were
based on a set of criteria that includes the following for each
compound: (a) electron impact (El) mass spectrum, (b)
chemical ionization (Cl) mass spectrum for molecular ion
confirmation, (c) elemental composition of major ions in the
El spectrum by means of low resolution, accurate mass
measurement, (d)comparison of mass spectra with authen-
tic speciments when available, and (e) comparison of GC
retention time with that of an authentic specimen when
available. Several factors in the analytical protocol of this
research were important because many of the compounds
identified are not available in mass spectral libraries. These
factors are the use of capillary GC columns, rapid MS scan
rates (generally 1 to 2 sec, compatible with the capillary GC
profiles), use of double-focusing mass spectrometer, and
the acquisition of accurate mass data without serious
compromise to sensitivity or scan speed by using low
resolution.
KMnO4 Oxidation and Base Hydrolysis
The structures and yields of more than 70 compounds were
determined in the product mixtures of fulvic and humic acid
fractions exposed to NaOH hydrolysis and/or KMnO*
oxidation (1,8). These products were classified, according to
structural similarity, into the six groups shown in Table 1.
The product distributions and overall yields for fulvic and
humic acid samples from the two different sources were
remarkably similar. The maximum yield of GC/MS detec-
table degradation products was approximately 25 wt% of
starting material. Loss of volatiles (presumably COz) during
oxidation was estimated at 20% to 25% of the original TOC,
so that overall accountability of degradation products can
be estimated as 35% of original TOC if it is assumed that
identified products average 50% carbon. Thus only about
one-third of starting material is represented by the identi-
fied compounds, though most of the chromatographable
material was identified (see Table 1).
Except for Black Lake fulvic acid, aliphatic dibasic acids
were the major base hydrolysis products for all the humic
acid and fulvic acid samples. All of the base hydrolysis
products identified were also present in permanganate
oxidation products, but carboxyphenylglyoxylic acids were
not found in the base hydrolyzed samples.
Permanganate oxidation of both fulvic and humic acids
produced benzenecarboxylic acids as the dominant identi-
fied product category with the tri-, tetra-, and pentacarboxy
acids presenting the principal substitution patterns. Fulvic
and humic acids also gave high relative yields of oxalic,
malonic, and succinic acids.
A significant difference was found among the aliphatic acid
products. Most of the monobasic acids and the long-chain
dibasic acids that were identified among the humic acid
oxidation products were not detected in those of fulvic acid
samples. This difference may indicate that the long-chain
acids were associated with the less soluble hydrophobia
humic acid macromolecules and were released as the
humic acid macromolecules were degraded.
Under the conditions of experiments conducted in this
study, the permanganate oxidation is believed to oxidize the
alkyl side chains of arenes (aliphatic-aromatic compounds)
and result in the formation of aromatic acids and saturated
aliphatic acids, the permanganate oxidation data indicate
that the principal number of alkyl constituents on the
aromatic rings in the humic macromolecule is in the range
of three to six to account for the predominance of the
benzenepolycarboxylic acid derivatives. Two facts support
the hypothesis that the length of these interaromatic alkyl
chains may be relatively short. First, the Cz-C* aliphatic
dibasic acids dominate the dibasic acid structures found.
Second, the increase of benzenecarboxylic acid yield for
KMnO4 (compared with NaOH hydrolysis) is significantly
greater than the increase in aliphatic dibasic acid yield. This
result could occur if some of the alkyl bridges were short
enough to yield only aromatic acids and CO2 after oxidation.
The survival of some long-chain dibasic acids after KMnO4
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Table 1. Summary of Results of KMnO4 Oxidation and NaOH Hydrolysis of Aquatic Humic Acidsand Fulvic Acids from Black Lake
and Lake Drummond*
Black Lake
Lake Drummond
Compound Class
KMnO, Oxidation NaOH Hydrolysis KMnOt Oxidation NaOH Hydrolysis
H/lf FA HA FA HA FA HA FA
Benzenecarboxylic acid methyl
esters (29 compounds)
Furancarboxylic acid methyl
esters (5 compounds)
Carboxyphenylglyoxylic acid methyl
esters (8 compounds)
Aliphatic monobasic acid methyl
esters (14 compounds)
Aliphatic dibasic acid methyl
esters (14 compounds)
Aliphatic tribasic acid methyl
esters (5 compounds)
Sum
Identified Percentage of
Total GC Peak Area
142.71 127.77 5.36
13.61 9.98 0 14
4.49
4.07
47.57
4.70 0.00
0.82 0.72
56.48 10.62
5.56 110.71 104.14 2.96
0.16 21.10 26.64 0.36
0.00 5.77 5.61 0.00
2.49
4.57
14.84
6.14 0.54
98.06 98.07 11.30
4.03
0.38
O.OO
1.99
5.66
0.62 1.47 0.29
21307 201.22 17.13
0.39 4.94 4.52 0.45 0.51
13.17 255.42 245.12 15.61 12,57
88
91
71
73
86
88
63
69
"Yields (mg) resulted from 1.0 g of starting humic samples.
\FA, fulvic acid: HA. humic acid.
is established by the complete data, but it is not possible to
evaluate the possibility that successive terminal oxidation
of longer alkyl substituents could produce the same result.
An attractive assumption is that most of the carboxyl groups
observed among these products constitute sites of carbon-
to-carbon linkages in the undegraded macromolecule. This
assumption is supported by the data in Table 1, which show
that the total yield of acids produced by base hydrolysis is
much lower. Some of the acid groups must be bound
originally in ester linkages, probably with other aromatic
moieties (to account for base hydrolysis yields). But most of
the alkyl constituents of aromatic rings must be carbon
chains, which resist sodium hydroxide hydrolysis. In
addition, some of the carboxylic acids must be present as
free groups in the undegraded macromolecule to account
for the acidity of aquatic humics.
In general, the predominant products found in Black Lake
samples are also the predominant products' in Lake
Drummond samples. Based on the results of this study,
aquatic humic materials from the two sources are believed
to be qualitatively similar, but quantitative variations were
observed in the composition of humic degradation mixtures
from the different sources. Whether these variations are
related to seasonal changes, various stages of the humi-
fication process, or vegetative conditions indigenous to the
source is not known.
Reaction with Chlorine
More than 100 reaction products were identified from
exposure of humic acid to chlorine at a pH of 12 and from
exposure of fulvic acid to chlorine at neutral pH (4,7,10,13).
Principal aliphatic products (only the C4 chain length and
less) are shown in Table 2. Concentrated ether extracts of
the fulvic acid reaction products were light green, had a
sweet/acid odor reminiscent of chloroform or some
chlorinated acid, and reacted vigorously with diazomethane.
Blank extracts were colorless, had no such odor, and had
little visible reaction with diazomethane. In these respects,
the concentrated fulvic acid samples and blanks resembled
their counterparts from the high-pH humic acid work.
The initial HOCI/C molar ratio for the neutral pH fulvic acid
reaction was 4, like that of pH 12 humic acid work. This pH 7
reaction with chlorine was apparently more rapid than the
pH 7 humic acid high-pH reaction, judging from the rates of
color bleaching. The pH 7 fulvic acid chlorine exposures
were therefore held 24 hr, while humic acid high-pH
exposures were allowed to reach 48 hr.
The majority of the pH 7 fulvic acid chlorine reaction
products contained chlorine, whereas most of the pH 12
humic acid chlorine reaction products did not. In addition,
many of the non-chlorine-containing fulvic acid products
were present in the system control or sample blank. An
adequate system control for the humic acid experiments
was impossible to obtain, but the reaction products
contained relatively large amounts of tatty acids (C16
dominant) that were not observed in the fulvic acid system
controls.
Nearly all of the products identified in the humic acid
experiment were methyl esters, presumably derived from
the methylation of mono- and polybasic acids. These
included mono- and dibasic, saturated and unsaturated,
chlorine-substituted and unsubstituted acids. Most of the
more than 100 compounds identified were not chlorinated;
however, di- and trichloroacetic acid, dichlorosuccinic acid,
and dichloromaleic and dichlorofumaric acid were formed
in especially high yield. A large number of mono- and
dibasic unchlorinated aliphatic acids from acetic and oxalic
acid up to the C2? monobasic fatty acid were identified. The
dibasic unchlorinated aliphatic acids were generally of low
molecular weight (C2-Cio). These aliphatic acids may be
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ring-cleavage products and were present in relatively low
yield. Benzenecarboxylic acids (including mono- to hexa-
carboxy acids in all isomers as well as small quantities of
methyl-substituted aromatic acids and isomers of
carboxyphenyl-glyoxylic acid) were also detected. Notice-
ably missing from the aromatic series were chlorine-
substituted aromatic acids and aromatic acids with aliphatic
side chains other than methyl. This pattern is similar to that
found with permanganate oxidation, suggesting that
chlorine in alkaline solution is capable of oxidizing side
chains down to terminal carboxyl groups on the aromatic
ring.
Several general features of the fulvic acid chlorination
product distribution can be stated. First, except for chloro-
form and chloral, all components were methyl esters. A
reasonable assumption is that they were free acids in the
original aqueous sample, which serves to explain the
diazomethane reaction. Second, unlike the pH 12 humic
acid chlorination products, most of the pH 7 fulvic acid
degradation products contained chlorine. They include
chloroform; chloral; methyl mono-, di-, and trichloroacetate;
dimethyl dichloromalonate; dimethyl dichlorosuccinate;
dimethyl dichloromaleate; methyl 2,2-dichloropropionate;
dimethyl chlorosuccinate; dimethyl chloromaleate; and
various other less abundant compounds. Even some
bromodichloromethane was formed, which must result
from bromide ion impurity activated by HOCI. No chlorinated
aromatic products were found.
Finally, most of the compounds from the fulvic acid
reactions not containing chlorine were aromatic. They
included various isomers of dimethylphthalate; benzene
tricarboxylic acid trimethyl ester; benzene tetracarboxylic
acid tetramethylester; and other aromatic methyl esters.
These compounds did not clearly result from the chlorina-
tion reaction, since the sample blank or system control
revealed their presence in similar quantities. Derivatives of
phenylglyoxylic acid were found in the chlorinated reaction
mixture (not in system control), an interesting group of
structures. Confirmation could not be achieved in these
samples, since no standards were available. They were
found in the humic acid chlorination product extract as well
as in potassium permanganate degradation product mix-
tures from aquatic humic and fulvic acids (10).,Liao et al.
proposed that such compounds can result from the oxida-
tion of fused ring systems present in the humic (or fulvic)
macromolecule (8).
A direct comparison of the yields of various compounds
from the fulvic and humic acid chlorinations is unrealistic,
since different reaction times were used. But both reactions
clearfy produce extremely similar products that contain a
predominance of small chlorinated acids. TOX analyses on
the concentrated ether extracts revealed that the fulvic
sample contained 60% more organically bound chlorine
than the humic sample, even though the reaction time of
the latter was twice as long. This observation agrees with
the expected greater electrophilic substitution of HOCM
present at the more acidic pH values compared to the OCI"
present at pH 12.
The yields of the four principal chlorination products of
fulvic acid were estimated initially by adding known
Table 2.
Short-Chain Chlorination Products of Aquatic
Humic and Fulvic Acids
Formula
Name
/Common)
Confidence*
CHC/3
CHBrCI2
CCI3CHO
H2CC/C02H
HCCI2CO2H
CCI3C02H
C#3CC/2CO2«
CCI2=CHC02H
CCI2=CCIC02H
H02CCCI2C02H
H02CfCHi)2C02H
HO2CCH2CHC/CO2H
H02CCC/2CH2CO2H
H02CCH=CCICO2H
H02CCC/=CCICO2H
H02CCCI=CC/CO2H
tnchoromethane
{chloroform)
bromodichloromethane
tnch/oroethanal
(chloral)
ch/oroethanoic acid
(chloroacetic acid)
dichloroethanoic acid
fdich/oroacetic acid)
trichloroethano/c acid
(trichloroacetic acid)
2,2-dichloropropanoic acid
3,3-d/ch/oropropenoic acid
trichloropropenoic acid
dichloropropanedioic acid
(dichloromalonic acid)
butanedioic acid
(succmic acid)
chlorobutanedioic acid
fchlorosuccintc acid)
2,2-dichlorobutanedioic acid
(2,2-dichlorosuccinic acid)
c\s-chlorobutenedioic acid
(ch/oroma/eic acid)
cis-dichlorobutenedioic acid
(dichloromaleic acid)
trans-dichlorobutenedioic acid
Idichlorofumanc acid)
*a. Confirmed El spectrum and GC retention time comparison with
authentic specimen.
b. Confirmed, El spectrum comparison with authentic specimen.
c Confident, El spectrum, Cl spectrum, no authentic specimen aval/able.
d Tentative, data relatively incomplete in some respect
t Observed only in fulvic acid samples
quantities of an internal standard (methyl-p-chlorobenzo-
ate) to ether extracts and measuring GC/MS peak-area
ratios derived from selected ion current chromatograms
(e.g., 117/139 for trichloroacetic acid). Actual weights of
compounds of interest were then calculated from standard
curves, and accurate concentrations in the aqueous
reaction mixture of the two principal products (trichloro-
acetic acid and chloroform) were then determined by
validated methods. An isotope dilution method developed in
our laboratory (13) was used for trichloroacetic acid, and
the standard EPA purge and trap method was employed for
chloroform.* Yield values are summarized in Table 3. The
values for the two minor products in Table 3 are probably
underestimated since they were determined only in the
ether extract.
The data establish that trichloroacetic acid (and not
chloroform) is the dominant reaction product, and that the
•Method 501 1, USEPA, Cincinnati, Ohio 45268
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Table 3. Yields of Fulvic Acid Chlorination Products
Product
mg mg Percent Percent
Product;'g Product C/g Original Final
Fulvic Acid Fulvic Acid C TOC TOX
Trichloroacetic acid
Chloroform
Dichloroacetic acid
Dichlorosuccmic acid
Total
90.3
382
102
3.4
142.1
133
3.8
1.9
09
19.9
30
0.8
0.4
02
44
32 1
17.3
36*
—
53.0
*Sum of dichloroacetic and dichlorosuccmic acids.
four chlorinated products shown in Table 3 collectively
account for 53% of the observed TOX (13).
Reaction with Other Oxidants
None of the other oxidants investigated in this study
produced appreciable amounts of degradation products
with aquatic fulvic acid compared with the permanganate
and chlorine product data. Small amounts of products were
identified with chlorine dioxide and ozone.
Reactions between CIO2 and fulvic acid at pH values of 3
and 7.8 were found to be rapid but limited. Neither
increased oxidant concentrations nor reaction times of up
to 24 hr seemed to influence the extent of reaction.
Recovery of TOC after reaction termination average 70%
under both pH conditions; thus, an average of 30% of the
original fulvic carbon was apparently converted to COa or
other extremely volatile compounds. The amount of ether-
extractable carbon was on the order of 10% to 14%; ethyl
acetate extracted an additional 3% to 4% of the original
carbon. The portion of this extractable carbon that was also
chromatographable was not determined, but it was evident
that identifiable products represented a small fraction of
the initial fulvic material. The bulk of the organic substrate
remained in aqueous solution, implying that it was not
sufficiently degraded to be analyzable by these techniques,
providing additional evidence that little overall reaction
occurred between CI02 and fulvic acid.
Four major classes of compounds were represented in the
degradation mixtures of both pH 3 and 7.8 reactions with
CIO2: benzenepolycarboxylic acid methyl esters, aliphatic
dibasic acid dimethyl esters, carboxyphenylglyoxylic acid
methyl esters, and aliphatic acid monomethyl esters.
Benzene di- and tricarboxylic acid methyl esters and
palmitic acid methyl ester, plus three of its branched
isomers, were dominant components of the sample ex-
tracts. But these aromatic compounds were also detected in
abundance in the undegraded control and therefore cannot
be regarded as unique products of the CI02 fulvic acid
reaction. Individual products or product abundances not
observed in system control samples included carboxy-
phenylglyoxylic acids, methylfurancarboxylic acid, dibasic
aliphatic acids (C4-Cio), and small quantities of dichloro-
acetic acid, monochloromalonic acid, and monochlorosuc-
cinic acid. The dibasic aliphatic acids were the one
structural category found in greater abundance with CI02,
than with permanganate and chlorine (2,9). The results
obtained with ozone were similar to those with CI02, except
that chlorinated derivatives were absent in product mixtures
(11). The cumulative ozone demand of fulvic acid varied
between 1 and 2 moles Oaper mole carbon. For experiments
in which a ratio of 5 moles Oaper mole carbon existed, 20%
of the original TOC was converted to C02 or other volatile
products.
Of the fulvic acid degradation agents tested, monochlor-
amine is apparently the least effective, since no reaction
products were identifiable in ether extracts of reaction
mixtures (12) (though fulvic acid solutions exerted a demand
of 0.13 mole of monochloramine per mole of fulvic carbon
after 24 hr at pH 9). Colclough et al. (2,9) observed by way of
comparison that fulvic acid consumed 0.3 mole CI02 per
mole of carbon at pH 7.8.
References
The following publications collectively contain the complete
findings of this research project. The Ph.D. thesis (#1, Liao)
is available from University Microfilms, P.O. Box 1346, Ann
Arbor, Ml 48106. Completed master's thesis (#2,3,
Colclough and Norwood) are available from R. F. Christman,
Department of Environmental Sciences and Engineering,
University of North Carolina, Chapel Hill, NC 27514. These
and articles that are in preparation (#11,12,13) are also
available from R. F. Christman.
1. Liao, Wenta, "Characterizaton of Aquatic Humic Sub-
stances," Ph.D. Dissertation, Department of Environ-
mental Sciencesand Engineering, University of North
Carolina at Chapel Hill, August 1981.
2. Colclough, Carol, "Organic Reaction Products of
Chlorine Dioxide and Natural Aquatic Fulvic Acids,"
M.S.P.H. Thesis, Department of Environmental Sci-
ences and Engineering, University of North Carolina
at Chapel Hill, December 1981.
3. Norwood, D. L, "A Comparison of GC/MS and
MS/MS for Complex Mixture Analysis," M.S.P.H.
Thesis, Department of Environmental Sciences and
Engineering, University of North Carolina at Chapel
Hill, December 1981.
4. Christman, R. F., Johnson, J. D., Pfaender, F. K.,
Norwood, D. L., Webb, M. R., Hass, J. R., and
Bobenrieth, M. J., "Chemical Identification of Aquatic
Humic Chlorination Products," In: Water Chlorina-
tion: Environmental Impact and Health Effects, Vol. 3,
Robert L. Jolley et al. (eds.), Ann Arbor Science
Publishers, Ann Arbor, Michigan, 1980.
5. Norwood, D. L., Johnson, J. D., Christman, R. F., Hass,
J. R., and Bobenrieth, M. J., "Reactions of Chlorine
with Selected Aromatic Models of Aquatic Humic
Material,"Environ. Sci. and Techno/. 14, 187, 1980.
6. Christman, R. F., Liao, W., Millington, D. S., and
Johnson, J. D., "Oxidative Degradation of Aquatic
Humic Material," In: Advances in the Identification
and Analysis of Organic Pollutants in Water, Vol. 2,
Lawrence H. Keith (ed.), Ann Arbor Science Pub-
lishers, Inc., Ann Arbor, Michigan, 1981.
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7. Johnson, J. D., Christman, R. F., Norwood, D. L, and
Millington, D. S., "Reaction Products of Aquatic
Humic Substances with Chlorine," Environ. Health
Perspectives. 46, 63-71, 1982.
8. Liao, Wenta, Christman, R. F., Johnson, J. D.,
Millington, D. S., and Mass, J. R., "Structural Char-
acterization of Aquatic Humic Material,"Environ. Sci.
and Techno/., 16, 402-410, 1982.
9. Colclough, C. A., Johnson, J. D., Millington, D. S., and
Christman, R. F., "Organic Reaction Products of
Chlorine Dioxide and Natural Aquatic Fulvic Acid," In:
Water Chlorination: Environmental Impact and Health
Effects, Vol. 4, Robert L. Jolley et al. (eds.), Ann Arbor
Science Publishers, Ann Arbor, Michigan, 1983.
10. Norwood, D. L, Johnson, J. D., and Christman, R. F.,
"Chlorinated Products from Aquatic Humic Material
at Neutral pH," In: Water Chlorination: Environmental
Impact and Health Effects. Vol. 4, Robert L. Jolley et
al. (eds.), Ann Arbor, Michigan, 1983.
11. Anderson, Linda, "Analysis of the Organic Reaction
Products of Aquatic Fulvic Acid Ozonation," M.S.P.H.
Thesis, Department of Environmental Sciences and
Engineering, University of North Carolina at Chapel
Hill, in preparation, 1983.
12. Jensen, James, "Identification of the Organic Pro-
ducts of the Reaction of Aquatic Fulvic Acid with
Monochloramine," M.S.P.H. Thesis, Department of
Environmental Sciences and Engineering, University
of North Carolina at Chapel Hill, in preparation, 1983.
13. Christman, R. F., Norwood, D. L, Millington, D. S.,
Johnson, D. J., and Stevens, A. A., "Identity and
Yields of Major Halogenated Products of Aquatic
Fulvic Acid Cnorination," submitted to Environ. Sci.
and Techno/., January 1983.
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